Answer:
2 posts
Step-by-step explanation:
Bob is going to build a deck that is 7 feet long and he is going to use posts that are 6 inches wide = 0.5 feet wide.
He is going to put the posts 6 feet apart and one on each end.
So the first thing will be a post 0.5 feet, and after 6 feet another post of another 0.5 feet, so if we add all of this will be:
0.5 feet + 6 feet + 0.5 feet = 7 feet
So he will only use 2 posts.
(See image)
